Aids to otology / by W.R.H. Stewart.

  • Stewart, W. R. H. (William Robert Henry), 1852-1906.
Date:
[1893]
Catalogue details

Licence: Public Domain Mark

Credit: Aids to otology / by W.R.H. Stewart. Source: Wellcome Collection.

    17/120 (page 13)
    The manubrium, or handle, runs downwards and backwards to below the middle of the tympanic membrane. The short 'process.—low conical eminence situated at the root of the handle. The long process runs from the junction of the handle and central portion downwards and forwards into the Glasserian fissure. The central portion articulates by a smooth depression (the head) with the next bone—the incus. The Incus, or anvil, sometimes called the Dens mollaris, situated behind the malleus, consists of a body and two processes. The body articulates with the malleus. The short process runs backwards to the posterior wall of the tympanum, to which it is connected by ligamentous fibres. The long process is directed downwards and articulates with the stapes. The Stapes, or stirrup, consists of— The head, articulating with the long process of the incus. The neck, receiving the insertion of the stapedius muscle. The base,—^An oval plate of bone attached to the margin of the fenestra ovalis. The cruras, the anterior of which is the shorter and straighter, diverge from the neck and are attached to the outer surface of the base, near its extremities. The Ligaments.—The ossicles are held together and in position by ligaments. The Muscles.—Two in number—the tensor tympani and the stapedius. The Tensor Tympani.—Arising from the cartilaginous end of the Eustachian tube and adjoining bony wall, is inserted into the inner part of the handle of the malleus. Action.—Prevents the membrane being pushed too far out, renders it more tense when the muscle contracts, and hence has been supposed to act as a damper, lessening the amount of vibrations of the membrane in the case of too-powerful sounds, or as a mechanism of accommodation, altering the membrane to the sounds that fall upon it. The muscle, actively regulated